The invention relates to a shoe structure and method of manufacturing such a structure having an upper comprising an outer material, a waterproof and water vapor permeable functional layer, a lining, an insole and an injection-molded sole. A lower edge of the upper has an extension comprising a porous and permeable material, and the insole is joined to this extension.
EP 0 298 360 A2 describes a shoe, wherein the outer material of an upper has an extension consisting of a porous, permeable material. It is expected that the resulting direct contact of the material of the sole with a functional layer will prevent penetration of water into a connecting seam joining an insole, a lining with a waterproof and water vapor permeable functional layer, and the extension of the upper.
It must be noted, however, that the density of the material of the sole changes during the flow of the still-liquid material of the sole through the extension of the upper consisting of a porous, permeable material. The material of the sole may begin to harden before an adequate joint with the functional layer is established. In such a case, a water bridge, extending to the connecting seam with the insole, forms between the functional layer and the material of the sole. Furthermore, it is been found that such shoes have poor antistatic properties.
Shoes having a sock-type lining, like those described, for example, in U.S. Pat. No. 4,599,810, have previously been suggested in order to ensure the watertightness of shoes. However, in addition to a problem of higher production costs, such shoes, particularly when used as safety shoes, show unacceptably poor antistatic properties. A static charge that frequently builds up on the wearer is discharged via the material to an unsatisfactory extent if the antistatic properties are poor, and not at all if the antistatic properties are very poor.
Embodiments of the present invention provide a shoe structure and method of making a shoe structure having an upper comprising an outer material, a waterproof and water vapor permeable functional layer, a lining, an insole and an injection-molded sole, wherein the waterproofing reliability and antistatic properties are improved and the cost of production is kept low.